Just checking in to see if this game is still as busted as it used to be years ago. It is.
The brother can gain points with the sister but you can never break the paths. There's no path with the two of them and the parents left to their being miserable. (Like they deserve). So since the game basically tells two stories concurrently, there's no escaping the destiny of that path. There's only two things you can do: The son can sleep with the cousin, rape the aunt and try to seduce his mom. Or he can ignore all that and try in vain at the sister just to end up with the mom trying to seduce him anyway. Not to mention that his point system is bogus to begin with. Lean into it, earn points, or don't, you end up at the same damn place in either storyline.
As the dad, I did everything I could to make up with the mother and ignore the daughter and he still has the same fantasies and sex dreams about her regardless of the points.
He may as well have designed this as a kinetic novel from the start.